As is known, the purpose of supercharging or turbocharging an internal combustion engine is to increase its horsepower output without increasing its speed. This is accomplished by increasing the mass flow rate over a naturally aspirated engine by pressurizing the intake gas. Supercharging uses crankshaft power to drive a compressor to accomplish this task; whereas turbocharging uses the energy of the exhaust gases, via a turbine, to drive a compressor to accomplish the same result. Since a supercharger is parasitic to engine performance (a gear-driven supercharger can use more than 20% of the total engine power at sea level), the turbocharger is considered superior for commercial road vehicles.
In the operation of a typical turbocharger, exhaust gases from the engine drive a turbine which, in turn, drives a compressor. Fresh air is taken from the outdoors, cleaned and mixed with the gasoline in the carburetor. The gasoline/air mixture is then compressed in the compressor and fed to the cylinders for combustion. In fuel-injection systems (e.g., diesel engines), on the other hand, the fuel is injected into the compressed air. For typical small passenger cars, the boost pressure is only about 9 pounds per square inch, but this is sufficient to double the peak horsepower.
Turbochargers currently in use suffer at least four main problems. First, when accelerating from a condition where the engine is idling with the vehicle at rest, the response is sluggish. This sluggish response has been termed "turbolag". What is needed is instantaneous response to full boost. Secondly, current turbochargers operate at some boost at all throttle conditions. What is needed is no boost at partial throttle conditions, and instantaneous boost at wide-open throttle, constant for all engine speeds. Thirdly, current turbochargers are lubricated with the engine oil. Dirt in the oil causes lubrication problems at the high-speed operation of the turbocharger (e.g., 100,000 RPM). Finally, current turbochargers are expensive. Conversion kits for non-turbocharged vehicles presently cost in excess of $1000.00.